Venting electric switch



Patented Feb. 23, 1932 UNITED STATES PATENT OFFICE GEORGE A. BURNHAM, OF SAUGUS, MASSACHUSETTS, ASSIGNOR TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPORA- TION OF MASSACHUSETTS VENTING ELECTRIC SWITCH Application filed A ru 14,

This invention relates to oil immersed electric switches, and particularly to cell-type switches, and the venting thereof.

When an oil immersed electric switch interrupts its circuit under heavy load, a large amount of oil gases and vapors may be generated within the switch casing and set up a substantial pressure herein. Under certain conditions of circuit interruption an explosive mixture may be formed within the switch casing and may explode and build up an exceedingly high internal pressure. It is highly desirable to relieve the switch casing of the gases and vapors generated upon circuit interruption whereby to keep down the pressure within the switch. Enclosed switches are usually provided with vent pipes or passages to carry the gaseous products resulting from circuitinterruption outof the enclosing casings. The vent pipes, however,

have usually been ofsuch a small size as seriou'sly to restrict the free escape of the gases as they are generated and so partially fail in their intended purpose.

' It is an object of this invention to provide an oil immersed electric switch and particularly an electric switch of the cell type with a vent pipe which extends from the switch to some remote locality where the switch gases "may be safely liberated, the vent pipe having such a large cross sectional area that the switch gases can freely escape from the switch casing as soon as they are formed without building up an undue pressure there- 1n.

A further object of this invention is the provisionof a fixed vent pipe which is adapted to be placed automatically into and out of communication with the switch casing when the switch is moved into and is withdrawn from operative position within its enclosing cell.

A further object of the invention is the provision of a venting system for an electric switch including a fixedly supported conduit having an opening adjacent the switch and a neck carried by the switch casing and adapted to be moved into and out of the conduitopening by the movements of the switch, whereby to connect the supporting conduit 1926. Serial No. 102,068.

with and disconnect it from communication with the interior of the switch casing automatically.

A yet further object of the invention is to provide oil separating means at the entrance of the conduit arranged to prevent the oil in the switch from escaping from the switch casing through the conduit.

A further object is generally to improve the construction and operation of electric switches.

Fig. 1 is a side elevation, partly in section, of a-switch cell and an oil immersed electric switch contained therein which is arranged to be vented according to this invention.

2 is a section taken along line 2-2 of Fig. 3 is an enlarged sectional elevation of the vent casing showing the arrangement of baflles in the oil separating chamber.

Fig. 4 is a section taken on line 4-4 of Fig. 3. V r J The switch herein shown embodying the invention is adapted to be enclosed in a suitable cell structure having the side walls 6, the rear wall 8, and the bottom wall 9. Said switch includes a casing comprising the oil receptacle 10 adapted to contain a body of oil or other suitable arc-quenching fluid, and the switch frame 12 which forms a top closure for said receptacle. Said switch frame comprises a cover section 13 which is adapted to support the stationary and movable switch members, which members may extend below said cover and into said oil in the usual manner.

Said stationary switch members include the relatively extensive insulating bushings 17 and 18 supported at a point intermediate their ends by suitable flanges 20 which flanges are secured to said cover section 13. Said bushing 18 may extend slightly higher than bushing 17 above said cover section 13 so that the terminal contacts adapted to be carried by the switch members will not interfere with each other as the switch is moved into and out of the cell. Conducting studs 21 are disposed within the axial passages through said bushings and are provided with contact blocks 22 at their lower ends.

across the end of said cover section 13.

The movable switch member comprises the switch operating rod 24 which is secured at its lower end to the brush or bridging member 25. Said operating rod is also connected 7 through suitable operating mechanism26 to oil by the separating contacts, and-these gases rise and fill the gas expansion space 28 above the'level of the oil in the receptacle. To prevent excessive pressure from building up withinthe casing and the possible ignition of the gases, said cover section 13 is provided with the rectangular vent opening 29 which is adapted to extend substantially vent opening 29 is surrounded on the. exterior of the casing by a metal vent-casing 30 to form the oil separating chamber 31. Said casing is provided with a peripheral outstanding flange 32 by which it is secured to the rear wall of said cover section 13. The rear wall of said vent casing 30 is adapted to taper and terminate in an annular collar or tube 33 0f substantial cross section. As here shown said vent casing and collar are formed of sheet metal although they may be otherwiseformed, if desired.

The switch casing is adapted normally to be in communication with a venting conduit '35 which conduit has a horizontal section 34 which is extendedthrough the rear wall 8 of the cell-structure and terminates in an opening into which said collar 33is received when the switch is in operative position within the. cell. Said conduit may be extendedv to anyv convenient location remote from the switch, for the .ultimateliberation of the switch gases, and is of substantial cross-sectional area, whereby to conduct the gases rapidly away and prevent building up any harmful amount of pressure within the switch 1 casing .due to the; accumulation of gases.

'Due to the rapidlty wlth whlch the gases are generated a great turbulence of the oil within the receptacle may result so that a considerable volume of oil may be thrown upward as the: gases rise .and frequently a part of the oil is carriedout of the casing through the usual vent by the outwardly rushing gases.

Consequently means is provided for separating the o lfrom the gases and thereby preventing the liquid oil from pass ingout of the casing with the gases, atthe same time preserving the free venting facilitiesof the switch casing.

Said separating'means includes a curved deflector 36 which is secured tosaid vent casing 30 b t "rivets or otherwise and extends across the ent re width ofsaid rectangular Said vent opening 29 and is so arranged as to guide the rising slugs of oil away from the vicinity of said vent opening. In this way, the greater bulk of oil which may be'hurled upwards will be prevented from escaping with the gases; Additional and staggered. baffle plates 36 and 37 are disposed in the path of the gas stream for the purpose of intercepting and trapping particles of oil-suspended 1n the 011 vapors and considerable gases. Sald plates maybe secured to the inner surface of saidvent casing by rivets or any other desired means. The free passage areathrough said vent casing about said baffle plates is adapted to be sufficiently large so that the baffle plates contained therein willnot restrict the passage of the gases through the venting conduit 34 therebeyond, but will pro: vide at least as large an area of passage as the rest of the ventingconduit. As the hot gases and oil vapor pass along the tortuous path between the cooling surfaces of said baflie plates, a large part of the condensible gas and most of the oil vapor will be cooled and condensed and will settle to the bottom of the i oil separating chamber 31' within saidvent casing 30 between. the lower baffle plates 37 and the oil can run back into the oil receptacle 10 througha series of smallvent holes 38 provided in the bottom of said baflie plates at suitable points.

-With the arrangement shown, the connection between the switch casing and the vent conduit is automatically made and broken as the switch is moved into operative position within the cell. and is withdrawn from such position, on its supporting wheels 40 and track 42- The opening of said conduitis flared and the collar 33 is guided by the truck wheels and track in its movements into and out of said opening. When in normal connected position,the collar is' adapted to be a loose sliding fit within the conduit, although the fit is adapted tobe sufficiently tight to prevent leakage of any large amount of liquid oil and oil gases.

fie

It is obvious that the structure may be modified in many ways without departing from the scope of the invention.

I claim: r

'1. In an oil-immersed electric switch the combination of an enclosing casing provided with a vent opening'in the uppenpart of its vertical side wall below the top, and means to prevent oil from being thrown from the switch through said opening, said means in cluding. a curved plate disposed in front of said opening within said casing and inclined upwardlyaway from saidopeningand 31? ran. ed to deflect an upwardly moving mass of oil away from said opening.

- r 2. In an'oil switch having an'enclosing casing adapted to contain oil and having a gas expansion. space over the o1l,a horlzontallydisposed venting conduit having lateral communication with said gas expansion space below the top of said casing, and means contained within said casing to prevent oil from being thrown from said casin into said conduit. said means including a eflecting plate disposed mainly within said casing and extended from the side wall thereof upwardly in front of and at an angle across the opening into said conduit and arranged to guide an upwardly moving mass of oil to move upwardly and laterally away from the opening.

In testimony whereof, I have signed my name to this specification.

GEORGE A. BURNHAM. 

